1. Field of the Invention
The present invention relates to a so-called projector-type vehicular headlamp and more particularly to a vehicular headlamp that performs overhead sign illumination.
2. Prior Art
Generally, in a projector-type vehicular headlamp, light from the light source, which is provided on an optical axis extending in the longitudinal direction of a vehicle, is reflected by a reflector forward (or toward the front) and toward the optical axis, and this reflected light is radiated forward of the lamp through a projection lens provided in front of the reflector.
When such a projector-type vehicular headlamp is constructed for low beam radiation, a shade 6 is employed. More specifically, as seen from FIG. 8, the shade 6 is provided between a projection lens 2 and a reflector 4 so that the shade 6 blocks partially the reflected light from the reflector 4, thus eliminating upwardly radiated light. As a result, a beam is radiated forward in the low beam light distribution pattern Pxe2x80x2 that has a predetermined cut-off line CLxe2x80x2.
In such a projector-type vehicular headlamp, since the shade 6 almost completely eliminates the upwardly radiated light, it becomes difficult to see the overhead sign OHS provided above the road ahead of the vehicle.
Therefore, as shown in FIG. 9, so as to solve such a problem, a projecting piece 8 is employed in a conventional vehicular headlamp. The projecting piece 8 is provided near the upper edge on the front surface of the shade 6 and extends obliquely downward in the forward direction. With this projecting piece 8, part of the reflected light from the reflector 4 is deflected and reflected upwardly, thus emitting overhead sign illuminating light Bxe2x80x2 that is directed upward through the projection lens 2.
However, the conventional vehicular headlamps described above have several problems.
Since the overhead sign illuminating light Bxe2x80x2 is obtained by way of partially reflecting the reflected light from the reflector 4 with the projecting piece 8, only a spot light distribution pattern is formed. It is thus not easy to obtain a light distribution pattern that has a shape and brightness appropriate for illuminating the overhead sign.
In addition, in the above-described conventional vehicular headlamp, since part of the light flux available for forming a low beam light distribution pattern Pxe2x80x2 is used as the overhead sign illuminating light Bxe2x80x2, loss of light flux occurs correspondingly.
Taking the foregoing problems into consideration, it is an object of the present invention to provide a projector-type vehicular headlamp which can obtain, without causing loss of light flux, a light distribution pattern that has a shape and brightness appropriate for overhead sign illumination.
The present invention accomplishes the above object with an improved structure for generating overhead sign illuminating light.
More specifically, the above object is accomplished by a unique structure for a vehicular headlamp of the present invention that includes: a light source which is provided on an optical axis extending in the longitudinal direction of a vehicle, a reflector which reflects light from the light source forward and towards the optical axis, a projection lens which is provided in front of the reflector, and a shade which is provided between the projection lens and the reflector and partially blocks the light reflected by the reflector so as to eliminate upwardly radiated light; and in the present invention, the shade is formed with:
an opening of a predetermined shape that penetrates through the (thickness of the) shade and is formed the upper edge of the shade, and
a visor-like shield provided on the back surface of the shade, the visor-like shield extending obliquely downward in the rearward direction from between the upper edge of the shade and the opening.
The specific structure of the xe2x80x9clight sourcexe2x80x9d is not particularly limited. The xe2x80x9clight sourcexe2x80x9d in the present application refers to a light discharging portion of a discharge bulb, a filament of an incandescent bulb such as a halogen bulb and the like.
The shape of the xe2x80x9copeningxe2x80x9d is not particularly limited to a particular shape as long as the opening is formed so as to penetrate through the (thickness of the) shade near the upper edge of the shade. The shape of the opening appropriately can be set according to the shape of a target light distribution pattern for overhead sign illumination and the like.
The specific structure of the xe2x80x9cvisor-like shield platexe2x80x9d, including shape, size, etc. is not particularly limited as long as the shield plate is provided on the back surface of the shade and extends obliquely downward in the rearward direction from between the upper edge of the shade and the opening. In addition, the visor-like shield plate can be constructed integrally to the shade or separately from the shade.
As described above, in the vehicular headlamp according to the present invention, a shade is provided between the projection lens and the reflector, so that it blocks part of the light reflected by the reflector and eliminates the upwardly radiated light. The shade has an opening of a predetermined shape that penetrates through the shade, and such an opening is formed near the upper edge of the shade. In addition, a visor-like shield plate that extends obliquely downward in the rearward direction from between the upper edge of the shade and the opening is provided on the back surface of the shade. Because of this structure, the vehicular headlamp of the present invention has several advantages.
First, among the light that is reflected by the reflector and reaches the shade, the light that has reached the opening is radiated forward through the opening. Since the opening is formed near the upper edge of the shade, a light distribution pattern, the shape of which corresponding to that of the opening, is formed at a location appropriate for overhead sign illumination by way of using the light radiated through the opening.
Since the visor-like shield plate that extends obliquely downward in the rearward direction from between the upper edge of the shade and the opening is provided on the back surface of the shade, among the light reflected by the reflector, only that reflected by the lower reflecting area of the reflecting surface is allowed to reach the opening. Thus, light flux radiated forward through the opening is restricted, and light flux of the overhead sign illuminating light is prevented from becoming excessively bright, and glare towards the driver of an oncoming vehicle and the like can be prevented.
As seen from the above, in the projector-type vehicular headlamp of the present invention, a light distribution pattern that has the shape and brightness appropriate for overhead sign illumination can be obtained without causing loss of light flux, and visibility of an overhead sign can be improved.
In the above-described structure, the lower reflecting area of the reflecting surface may have the shape of a normal reflecting surface of a reflector used in projector-type vehicular headlamps. It is, instead, also possible to form at least one reflective element, which reflects light from the light source towards the opening, in an area below the position where the reflecting surface and an imaginary plane that extends downward from the shield plate intersect or meet. This structure has several advantages.
With such a structure of the present invention, since the visor-like shield plate is provided, a reflecting area (i.e. a reflecting area in which the reflected light is not directed forward over the shade) that makes no contribution to the formation of the low beam light distribution pattern can be formed within the lower reflecting area of the reflecting surface. Moreover, such a reflecting area can have a reflecting surface shape that is formed only with a consideration of overhead sign illumination.
Thus, with at least one reflective element that reflects light from the light source towards the opening and is formed in an area below the intersection position of the reflecting surface and an imaginary plane that extends downward from the shield plate, a light distribution pattern that has a light intensity distribution appropriate for overhead sign illumination is obtained, and the visibility of an overhead sign is considerably improved.
Furthermore, by way of forming a plurality of diffuse reflective elements in the peripheral area of the reflective element on the reflecting surface, the ratio of the reflected light (among the reflected light from the peripheral area) which is radiated forward through the opening becomes smaller. Accordingly, unnecessary expansion of the light distribution pattern for overhead sign illumination by the reflected light from such a peripheral area is prevented, and as a result, the generation of glare light is prevented.